The present invention relates to building construction wherein corner bead is used for forming smooth transition contours between plaster and plasterboard wall surfaces, and more particularly to facilitating the use of "bullnose" beading having relative large convex corner radii together with base and/or crown molding at floor and ceiling extremities of the corner bead and like features that are inconvenient or impractical in combination with typical bullnose corner radii.
Bullnose corner beading, popularly used at convex wall surface intersections in several styles of building construction, has a corner radius typically ranging from 0.5 inch to 0.75 inch, the corner radius subtending an angle of approximately 90.degree., and flanges extending in slightly offset relation to opposite extremities of the corner contour surface. The beading is usually nailed through the flanges against intersecting wallboard surfaces, and a plaster-like material is trawled over the flanges for creating smoothly finished surfaces extending from the wallboard to the respective extremities of the corner contour surface, the beading providing trawling guides along the contour surface extremities.
The large corner radius of bullnose beading makes application of molding strips such as base and crown molding particularly difficult in that the molding, being rigid or nearly so, cannot be formed to follow the contour of the corner bead, and without such forming, a large gap is created between the beading and the molding. There have been attempts to facilitate forming conventional wooden base and crown molding to follow the bullnose contour by cutting skarfs across the grain from the back side of the molding. The resulting appearance is unsatisfactory, not only because the skarfs penetrate through contoured portions of the molding, but also because pieces of the molding split from the strip when it is nailed in place.
Attempted solutions to these problems have been unsatisfactory for a number of reasons. In one example of the prior art, end portions of the corner bead are molded as separate pieces of plastic, having a transition contour to a plain angle profile and a portion having the plain angle configuration for extending under the base or crown molding. However, the resulting joint between the separate plastic pieces and the main bullnose section is unsightly, being impossible to hide completely, even with careful filling. Also, the molded pieces must either be made and stocked in different lengths to match the various base and crown moldings in use, or they must be cut to length on the job at added expense. A variation not having the plain angle portion is possible, but it is impractical to vertically locate the piece properly to butt against the molding, the molding being applied in a later stage of the construction.
Bullnose corner bead is also available as a single member having a plain angle end portion formed therein, the corner bead being supplied in oversize lengths for permitting the plain angle end portion to be trimmed to a suitable length for use with base molding, the opposite end of the corner bead also being trimmed for producing the required overall length. This scheme also has a number of disadvantages, for example:
1. The corner bead is significantly more expensive to provide than standard lengths having a uniform bullnose contour;
2. There is extra labor in cutting both ends of the corner bead;
3. There may be situations wherein the preformed plain angle end portion is too short; and
4. There is no provision for the use of both base and crown molding;
Thus there is a need for inexpensive bullnose corner bead that is compatible with both base and crown molding of variant widths.